Endoprosthesis having foot extensions

ABSTRACT

Endoprosthesis, such as a stent, includes at least one annular element defined by a first set of strut members interconnected to define apices proximate opposite sides of the annular element. The annular element further includes a foot extension extending between at least one pair of circumferentially-adjacent strut members. The foot extension has first and second foot portions extending circumferentially from corresponding ends of the circumferentially-adjacent strut members, and are contoured to provide at least two areas of flexure. The first and second foot portions are joined at a toe portion of the foot extension, and define a circumferentially-directed apex between the pair of circumferentially-adjacent strut members. Preferably, at least one or more additional annular elements, each defined by interconnected strut members, are provided. The annular elements are generally expandable between a delivery configuration and a deployed configuration. The annular elements are longitudinally aligned and connected at connection locations. Preferably, each connection location includes a foot extension, such as by an overlapping pattern between the longitudinally-adjacent annular elements or by a connector extending therebetween.

RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 10/430,644 May 6, 2003, now U.S. Pat. No. 7,128,756the entirety of which is herein incorporated by reference. Thisapplication claims the benefit of U.S. patent provisional applicationSer. No. 60/378,346 filed May 8, 2002, and of U.S. patent applicationSer. No. 60/379,593 filed May 8, 2002; each of which is expresslyincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to an endoprosthesis for delivery anddeployment within a body vessel of a human or animal. More particularly,the invention relates to a stent including at least one annular elementhaving one or more foot extensions for improved performancecharacteristics.

BACKGROUND OF THE INVENTION

Stents, grafts and a variety of other endoprostheses are well known andused in interventional procedures, such as for treating aneurysms, forlining or repairing vessel walls, for filtering or controlling fluidflow, and for expanding or scaffolding occluded or collapsed vessels.Such endoprostheses can be delivered and used in virtually anyaccessible body lumen of a human or animal, and can be deployed by anyof a variety of recognized means. One recognized indication ofendoprostheses, such as stents, is for the treatment of atheroscleroticstenosis in blood vessels. For example, after a patient undergoes apercutaneous transluminal coronary angioplasty or similar interventionalprocedure, an endoprosthesis, such as a stent, is often deployed at thetreatment site to improve the results of the medical procedure and toreduce the likelihood of restenosis. The endoprosthesis is configured toscaffold or support the treated blood vessel; if desired, theendoprosthesis can also be loaded with beneficial agent so as to act asa delivery platform to reduce restenosis or the like.

The endoprosthesis is typically delivered by a catheter delivery systemto a desired location or deployment site inside a body lumen of a vesselor other tubular organ. To facilitate such delivery, the endoprosthesismust be capable of having a particularly small cross profile to accessdeployment sites within small diameter vessels. Additionally, theintended deployment site may be difficult to access by a physician andoften involves traversing the delivery system through the tortuouspathway of the anatomy. It therefore is desirable to provide theendoprosthesis with a sufficient degree of longitudinal flexibilityduring delivery to allow advancement through the anatomy to the deployedsite.

Once deployed, the endoprosthesis should be capable of satisfying avariety of performance characteristics. The endoprosthesis should havesufficient rigidity or outer bias when deployed to perform its intendedfunction, such as opening a lumen or supporting a vessel wall.Similarly, the endoprosthesis should have suitable flexibility along itslength when deployed so as not to kink or straighten when deployed in acurved vessel. It also may be desirable to vary the rigidity orflexibility of the endoprosthesis along its length, depending upon theintended use. Additionally, it may be desirable for the endoprosthesisto provide substantially uniform or otherwise controlled coverage, e.g.,as determined by the ratio of the outer surface of the endoprosthesis tothe total surface of the vessel wall along a given length. For example,increased coverage may be desired for increased scaffolding, whereasdecreased coverage may be desired for side access to branch vessels.Control of the cross profile and length of the endoprosthesis upondeployment also is desirable, at least for certain indications.

Numerous designs and constructions of various endoprosthesis embodimentshave been developed to address one or more of the performancecharacteristics summarized above. For example, a variety of stentdesigns are disclosed in the following patents: U.S. Pat. No. 4,580,568to Gianturco; U.S. Pat. No. 5,102,417 to Palmaz; U.S. Pat. No. 5,104,404to Wolff; U.S. Pat. No. 5,133,732 to Wiktor; U.S. Pat. No. 5,292,331 toBoneau; U.S. Pat. No. 5,514,154 to Lau et al.; U.S. Pat. No. 5,569,295to Lam; U.S. Pat. No. 5,707,386 to Schnepp-Pesch et al.; U.S. Pat. No.5,733,303 to Israel et al.; U.S. Pat. No. 5,755,771 to Penn et al.; U.S.Pat. No. 5,776,161 to Globerman; U.S. Pat. No. 5,895,406 to Gray et al.;U.S. Pat. No. 6,033,434 to Borghi; U.S. Pat. No. 6,099,561 to Alt; U.S.Pat. No. 6,106,548 to Roubin et al.; U.S. Pat. No. 6,113,627 to Jang;U.S. Pat. No. 6,132,460 to Thompson; and U.S. Pat. No. 6,331,189 toWolinsky; each of which is incorporated herein by reference.

Although the various designs for endoprostheses that have been developedto date may address one or more of the desired performancecharacteristics, there a remains need for a more versatile design for anendoprosthesis that allows improvement of one or more performancecharacteristics without sacrificing the remaining characteristics.

SUMMARY OF THE INVENTION

The purpose and advantages of the present invention will be set forth inand are apparent from the description that follows, as well as will belearned by practice of the invention. Additional advantages of theinvention will be realized and attained by the methods and devicesparticularly pointed out in the written description and claims hereof,as well as from the appended drawings.

To achieve these and other advantages in accordance with the purpose ofthe invention, as embodied herein and broadly described, the inventionincludes an endoprosthesis for delivery and deployment in a body lumen.The endoprosthesis includes at least one annular element defined by afirst set of interconnected strut members, wherein each strut member hasa first end and a second end. Preferably, the first end of selectedcircumferentially-adjacent strut members are interconnected to defineapices proximate a first longitudinal side of the first annular elementand the second end of selected circumferentially-adjacent strut membersare interconnected to define apices proximate a second longitudinal sideof the first annular element. The annular element further includes afoot extension extending between a pair of circumferentially-adjacentstrut members. The foot extension has a first foot portion extendingcircumferentially from the first end of one of thecircumferentially-adjacent strut members of the pair and a second footportion extending circumferentially from the first end of the other ofthe circumferentially-adjacent strut members. The first and second footportions are joined at a toe portion of the foot extension, andgenerally define an apex between the pair of circumferentially-adjacentstrut members.

Preferably, the endoprosthesis of the invention further includes asecond annular element defined by a second set of interconnected strutmembers, wherein each strut member of the second annular element alsohas a first end and a second end. Circumferentially-adjacent strutmembers are interconnected to define apices on opposite sides of thesecond annular element. The first annular element and the second annularelement are aligned longitudinally adjacent to each other along alongitudinal axis and connected to each other at at least one connectionlocation. The second annular element also can include a foot extension.Additional annular elements also can be provided.

The annular elements are generally expandable between a deliveryconfiguration and a deployed configuration. Each annular element can bedefined as a continuous closed ring, or as a coiled sheet or the like.Preferably, each strut member is a straight member, aligned to besubstantially parallel with the longitudinal axis of the endoprosthesiswhen in the delivery configuration. Selected strut members can have auniform width or can have varied width, such as a continuous taper orincreased midsection width between the opposite ends of the strutmember. The apices on either side of each annular element that are notdefined by a foot extension can have a V-shape, an arcuate shape, oranother shape as desired.

The foot extension is contoured to provide at least two areas offlexure, and extends circumferentially at an angle relative to thelongitudinal axis of the annular element. The foot extension can includestraight portions, curved portions or combinations thereof to define anankle portion, a toe portion, a base portion and a heel portion. Thebase portion can be a straight member, or contoured as a V-shape or thelike. In a preferred embodiment, the foot extension has an average widthgreater than that of the remaining strut members of the annular element.With the foot extension located between longitudinally-adjacent annularelements, the base portion of the foot extension generally faces thelongitudinally-adjacent annular element.

Preferably, the connection location between the longitudinally-adjacentannular elements includes the foot extension. By providing theconnection location at the base portion of the foot extension, theapices proximate a side of the first annular element generally can bearranged circumferentially out of alignment, or less than 180 degreesout of phase, with the apices proximate a facing side of the secondannular element. The connection location can be defined by anoverlapping pattern between the longitudinally-adjacent annularelements, such as the base of a foot extension on one annular elementand a corresponding apex on the other annular element. Alternatively,the connection location can include a connector extending between theannular elements. The connector can be a straight member or a shapedmember, with opposites ends circumferentially either in or out ofalignment, as desired. In a preferred embodiment, the connector has anL-shape, with one leg longer than the other leg. In a preferredembodiment, a plurality of connection locations are provided between theadjacent annular elements, with a foot extension provided at some or allof the connection locations. The plurality of foot extensions can allextend in the same circumferential direction, or can be arranged toextend in opposing circumferential directions.

A radiopaque material preferably is incorporated in at least a portionof the endoprosthesis. For example, at least one of the annular elementscan comprise radiopaque material. Alternatively, radiopaque markers canbe attached to at least one of the annular elements, or the annularelements can be formed of radiopaque material. As another example, atleast one of the annular elements can be formed with a first layer ofbase material and a second layer of radiopaque material.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and are intended toprovide further explanation of the invention claimed.

The accompanying drawings, which are incorporated in and constitute partof this specification, are included to illustrate and provide furtherunderstanding of the device of the invention. Together with thedescription, the drawings serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a representative embodiment, in planar format, of anendoprosthesis in accordance with the invention.

FIGS. 2 a through 2 e show detail views, in planar format, of variousexemplary foot extensions in accordance with the present invention.

FIGS. 3 through 10 show alternative representative embodiments of thepresent invention in planar format, each of an endoprosthesis havingannular elements connected at a plurality of connection locations byconnectors.

FIGS. 11 through 13 show detail views of various connector alternatives.

FIGS. 14 a through 14 e show detail views, in planar format, of variousalternative connector relationships between adjacent annular elements.

FIGS. 15 through 25 show alternative representative embodiments of thepresent invention in planar format, each of an endoprosthesis havingannular elements connected at a plurality of connection locationswithout connectors.

FIGS. 26 and 27 a through 27 d are detail views, in planar format,showing various embodiments of overlapping patterns of adjacent annularelements defining connection locations.

FIG. 28 shows a representative embodiment, in planar format, of anendoprosthesis configured to have varied characteristics along itslength.

FIGS. 29 a through 29 f respectively show a preferred embodiment of aself-expanding stent in accordance with the present invention, (a) inplanar format, (b) in a front-half side view as cut and polished from atube, (c) in a front-half side view of a delivery configuration, (d) ina front-half side view of a deployed configuration, (e) in a perspectiveview of a deployed configuration, and (f) in a side view as deployed ina curved vessel.

FIGS. 30 a through 30 f respectively show a preferred embodiment of aballoon expandable stent in accordance with the present invention, (a)in planar format, (b) in a front-half side view as cut and polished froma tube, (c) in a front-half side view of a delivery configuration, (d)in a front-half side view of a deployed configuration, (e) in aperspective view of a deployed configuration, and (f) in a side view asdeployed in a curved vessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, an endoprosthesis is providedfor delivery within a body lumen of a human or animal. Theendoprosthesis can include, but is not limited to, stents, grafts,valves, occlusive devices, trocars, aneurysm treatment devices, or thelike. The endoprosthesis of the present invention can be configured fora variety of intralumenal applications, including vascular, coronary,biliary, esophageal, urological, gastrointestinal or the like.

Generally, the endoprosthesis of the present invention includes a firstset of interconnected strut members defining a first annular element,wherein each strut member of the first annular element include a firstend and a second end. The endoprosthesis also includes a foot extensionextending between a pair of circumferentially-adjacent strut members. Asdescribed further below, the foot extension has a first foot portionextending circumferentially from the first end of one of thecircumferentially-adjacent strut members and a second foot portionextending circumferentially from the first end of the other of thecircumferentially-adjacent strut members. The first and second footportions are joined at a toe portion of the foot extension.

Preferably, and as embodied herein, the endoprosthesis further includesat least a second set of interconnected strut members defining a secondannular element. The endoprosthesis can include additional annularelements defined by interconnected strut members as desired or needed.Each annular element generally defines a structure extendingcircumferentially about a longitudinal axis. The cross profile of eachannular element preferably is at least arcuate, and more preferablyeither circular or spiral, although alternative cross profiles, such asrectilinear or the like, can be used if desired.

The first annular element is aligned longitudinally adjacent to thesecond annular element along the longitudinal axis, and connected toeach other at at least one connection location. Preferably, the firstand second annular elements generally define a tubular structure. Forexample, each annular element can define a continuous closed ring suchthat the longitudinally-aligned annular elements form a closed tubularstructure having a central longitudinal axis. Alternatively, eachannular element can define an open ring such that a rolled sheet or opentubular type structure is defined by the annular elements. Furthermore,each annular element can define a 360 degree turn of a helical pattern,such that the end of one annular element can be joined with thecorresponding end of a longitudinally-adjacent annular element to definea continuous helical pattern along the length of the endoprosthesis.

Each strut member of the annular elements includes a first end and asecond end. The strut members of each annular element are disposedcircumferentially adjacent to each other, and interconnected so as todefine an expandable structure. For example, and with reference to theclosed tubular structure above, circumferentially-adjacent strut membersof each annular element can be interconnected, either directly orindirectly, in an end-to-end format to define a continuous ring having agenerally circular cross profile. By altering the angle or distancedefined between circumferentially-adjacent strut members, the tubularstructure can be radially expanded between a delivery configuration anda deployed configuration. As discussed in detail below, the expandablestructure can be expanded by the application of an external force, suchas by a balloon, or by a change in delivery conditions, such as anincrease in temperature or the removal of a restraint, so as to allowthe structure to self expand.

With reference to FIG. 1, for purpose of illustration and notlimitation, a representative embodiment of an endoprosthesis 100 of thepresent invention in a deployed configuration is depicted in a planarformat for clarity. As shown in FIG. 1, the endoprosthesis includes aplurality of annular elements 10 aligned longitudinally adjacent to eachother along a longitudinal axis 15. Although only one annular elementneed be provided in accordance with the invention, it is preferable thatthe endoprosthesis includes a plurality of annular element 10, depictedherein for purpose of illustration by at least a first annular element10′ and a second annular element 10″.

Each annular element includes a set of interconnected strut members 20,which are disposed circumferentially about longitudinal axis 15. Eachstrut member has a first end 22′ and a second end 22″, referencedgenerally as end 22. The first end 22′ of selectedcircumferentially-adjacent strut members 20 are interconnected to defineapices 30 proximate a first longitudinal side 12 of each annular element10, and the second end 22″ of selected circumferentially-adjacent strutmembers 20 are interconnected to define apices 30 proximate a secondlongitudinal side 14 of the annular element. In this manner, eachannular element 10 can be expanded to a deployed configuration as shownin FIG. 1 by altering or “opening” the angle defined betweencircumferentially-adjacent strut members 20. It also is recognized inthe embodiment of FIG. 1 that circumferentially-adjacent apices 30 oneach side 12, 14 of the annular element 10 are spaced apart by acircumferential distance D, such that each annular element is expandedby increasing the distance D between circumferentially-adjacent apices30. At any given condition between the delivery configuration and thedeployed configuration, the distance D can be balanced or constant fromone set of circumferentially-adjacent apices to the next, or can bevaried if desired.

As shown in FIG. 1, certain apices 30 on each side of the annularelement 10 can be defined by interconnecting corresponding ends 22 ofcircumferentially-adjacent strut members directly together to form azig-zag pattern of alternating V-shapes when deployed. Alternatively, anapex member can be provided between the corresponding ends of adjacentstrut members to form a contoured apex, such as by using a straight apexmember to form a flat apex as disclosed in U.S. Pat. No. 6,113,627 toJang, or a curved apex member to form an arcuate apex as disclosed inU.S. Pat. No. 5,514,154 to Lau.

In the representative embodiment of FIG. 1, the strut members 20 of eachannular element 10 are interconnected with adjacent strut members 20 toform a continuous closed ring, such as depicted more clearly in FIGS. 29e and 30 e. As previously noted, however, each annular element candefine an open ring to form a rolled sheet or open tubular typestructure as described further with regard to FIG. 3, or can defineadjacent turns of a continuous helical pattern as described with regardto FIG. 25, for purpose of illustration.

FIG. 1 also depicts each strut member 20 of the annular element 10 as astraight member. Preferably, when in the delivery configuration, thestraight strut members 20 are generally aligned parallel with thelongitudinal axis 15, as well as with each other, as shown for examplein FIGS. 29 c and 30 c. Although not shown, alternative strut membershapes can be used in addition to or in lieu of the straight strutmembers, such as L or V-shaped strut members or the like as is known inthe art. Also, the number of strut members included in each annularelement will depend upon the size and desired characteristics of theendoprosthesis. For example, a greater number of strut members andinterconnecting apices can be provided for increased coverage of thevessel wall by the endoprosthesis or increased cross profile of theendoprosthesis in the deployed configuration.

Similarly, the radial bias or rigidity of each annular element can becontrolled or varied by altering the shape or size of the strut members.For example, radial bias or rigidity of an annular element, whendeployed, generally can be increased by decreasing the length or bymodifying the cross sectional profile of selected strut members of theannular element. It therefore is possible to provide an endoprosthesisin accordance with the present invention having varied radial bias orrigidity along its length by providing one annular element with a radialbias or rigidity that is different from the radial bias or rigidity ofanother annular element as shown in FIGS. 12 b and 28 and describedfurther below. In a similar manner, it is possible to provide anendoprosthesis having a tapered or flare shape formed of adjacentannular elements having different cross profiles when in the deployedconfiguration but similar or uniform radial bias or rigidity along itslength.

Further in accordance with the present invention, and as previouslynoted, at least one annular element includes a foot extension extendingbetween at least one pair of circumferentially-adjacent strut members.The foot extension can thus define an apex between the pair ofcircumferentially-adjacent strut members of the annular element. Thefoot extension includes a first foot portion extending circumferentiallyfrom an end of one of the adjacent strut members and a second footportion extending circumferentially from a corresponding end of theother of the circumferentially-adjacent strut members. In combination,the first and second foot portions generally define an ankle portion, atoe portion, a base portion and a heel portion of the foot extension,which in combination define a generally circumferentially-directed apex.

With reference to the exemplary embodiment of FIG. 1, for illustrationand not limitation, foot extension 40 extends between a pair 24 ofadjacent strut members 20 of each annular element 10. As depicted forpurpose of illustration, the foot extension 40 includes a first portion41 extending circumferentially from an end 22 of one of the adjacentstrut members 20, and a second portion 43 extending circumferentiallyfrom the corresponding end 22 of the other of the adjacent strut members20. The juncture of the first and second foot portions 41, 43 defines acircumferentially-extending toe portion 48 of the foot extension 40.Similarly, and for purpose of discussion and not limitation, FIG. 1shows that an ankle portion 44 is defined proximate the juncture of thefirst foot portion 41 with one of the circumferentially-adjacent strutmembers 20, and that a heel portion 42 is defined proximate the junctureof the second foot portion 43 with the other of thecircumferentially-adjacent strut members 20. The toe portion 48 extendsin a first circumferential direction a distance greater than the heelportion 42 of the foot extension 40 extends in an oppositecircumferential direction. In the embodiment of FIG. 1, the entirety ofthe foot extension 40 extends in the circumferential direction of thetoe portion 48. Furthermore, at least one of the first and second footportions 41, 43 defines a base portion 46 at or proximate to thecorresponding side 12 or 14 of the annular element 10. Defined generallywithin the boundary of the first and second portions 41, 43 is an openfoot region 49 (see also, FIG. 2 a).

A variety of configurations can be used for the foot extension inaccordance with the present invention. For purpose of illustration andcomparison with the foot extension of FIG. 1, exemplary embodiments ofvarious alternative foot extension configurations are depicted in FIGS.2 a through 2 e.

For example, the foot extension of the invention generally extends fromthe pair of circumferentially-adjacent strut members circumferentiallyat an angle relative to a line parallel to the longitudinal axis of theannular element. FIG. 1 shows a foot extension generally extendingcircumferentially at an angle of about 90 degrees relative to thelongitudinal axis 15. However, the foot extension can be configured toextend circumferentially at an angle of less than 90 degrees relative tothe longitudinal axis, as shown for example in FIG. 2 a.

Additionally, FIG. 1 shows a foot extension 40, wherein the first footportion 41 and the second foot portion 43 are generally parallel,straight elongate portions joined by curved portions. Particularly, thebase portion 46 is defined by a generally straight portion and each ofthe toe portion 48, the ankle portion 44 and the heel portion 42 isdefined by a curved portion. Each portion of the foot extension 40, aswell as each of the circumferentially-adjacent strut members 20, has asubstantially uniform width W and thickness in the embodiment of FIG. 1.In this manner, the circumferentially-adjacent strut members 20 will besubstantially parallel to the longitudinal axis 15 and to each other,and region 49 will be substantially closed when in the deliveryconfiguration. As depicted in FIG. 1, the foot extension 40 will thusgenerally define at least two areas of flexure between the pair ofcircumferentially-adjacent strut members 20; that is, one at the heelportion 42 and one at the ankle portion 44. An additional, oralternative, area of flexure can be defined at the toe portion 48 ifdesired to facilitate further expansion between the pair ofcircumferentially-adjacent strut members 20, such as to define a threepoint hinge configuration.

FIG. 2 a depicts a preferred embodiment of a foot extension similar tothat of FIG. 1. As previously noted, however, the foot extension 40 ofthis embodiment extends circumferentially at an angle

less than 90 degrees relative to the longitudinal axis 15. Additionally,the first and second foot portions 41, 43 are generally parallel butspaced apart to define a relatively more open region 30 than that of thefoot extension of FIG. 1. To control expansion of the annular element,the width of the foot extension and circumferentially-adjacent strutmembers can be varied accordingly. For example, and as previously noted,circumferentially-adjacent apices along each side of the annular element10 are spaced apart by a circumferential distance D, wherein thedistance D generally increases as the annular element is expanded. It isoften desirable to balance an annular element so as to expand uniformly,wherein the distance D increases a similar amount and at a similar ratebetween each pair of circumferentially-adjacent apices. Due to theincreased flexure facilitated by the foot extension similar of FIG. 1,the distance Df between the circumferentially-adjacent apices located atthe end of the pair 24 of circumferentially-adjacent strut members 20opposite the foot extension 40 can increase to an extent or at a rategreater than the distance Da between other circumferentially-adjacentapices of the annular element. By providing the first and second footportions 41, 43 of the foot extension with an average width greater thanthe average width of the circumferentially-adjacent strut members 20, asshown in FIG. 2 a, the expansion between the circumferentially-adjacentapices 30 can be controlled or even balanced if desired. For example,and as shown in FIG. 2 a, the first and second foot portions 41, 43 canbe provided with a substantially constant width. Alternatively the firstfoot portion 41 can be provided with a width W1 different than that W2of the second foot portion 43.

As previously noted with regard to the exemplary embodiment of FIG. 1,the circumferentially-adjacent strut members 20 and the differentportions of the foot extension 40 can be provided with a substantiallyuniform width and thickness throughout. If the foot extension isprovided with an increased width, it may be desirable or necessary todistribute stress or eliminate stress concentrations in the pair ofcircumferentially-adjacent strut members 20. As embodied in FIG. 2 a, atleast one or both strut member 20 of the pair 24 ofcircumferentially-adjacent strut members can be provided with a variedwidth. For example, and as shown in FIG. 2 a, each strut member of thepair 24 of circumferentially-adjacent strut members can be tapered froma first width W′ substantially similar to or even greater than that ofthe foot extension at the first end 22′ of the strut member to a secondwidth W″ substantially similar to or even greater than that of theadjacent strut member 20 connected at the second end 22″.

To further control expansion of the annular element, selected apicesalong the same longitudinal side 12, 14 of the annular element 10 as thefoot extension also can be modified. For example, an apex 30 can berelaxed by reducing its width to facilitate greater expansion, orstiffened by increasing its width to facilitate less expansion. As shownin FIG. 2 a, the width of selected apices 30 rw are reduced to relax theapex 30 and thus control, such as balance, expansion of the annularelement as needed or desired.

Furthermore, selected apices on the same side of the annular element asthe foot extension can be configured to accommodate additional features.For example, and in accordance with another aspect of the presentinvention, it is desirable to enhance retention of a balloon expandableendoprosthesis on a balloon delivery system. As shown in FIG. 2 a, thefoot extension 40 extends in a first circumferential direction, and acircumferentially-adjacent apex 30 a is located proximate the footextension 40 in the first circumferential direction. When in thedelivery configuration, this circumferentially-adjacent apex 30 a islongitudinally aligned with, and preferably can substantially contact,the toe portion 48 of the foot extension so as to define a gap G betweenthe circumferentially-adjacent strut members 20. Balloon material of thedelivery system thus can be captured within this gap G, during crimpingor through known heat treatment techniques, to enhance stent retentionon a balloon. Additionally, or alternatively, a gap can be definedwithin an enlarged region 49 of the foot extension 40 for similar stentretention purposes if desired.

FIG. 2 b depicts yet another foot extension configuration in accordancewith the invention. The first foot portion 41 of the foot extension 40is generally angled relative to the second foot portion 43, rather thanaligned in parallel as shown in FIG. 1. Additionally, the second footportion 43 is generally V-shaped to define a base portion 46 extendingsubstantially perpendicular to the longitudinal axis, but with a moreangular heel portion 42 than that of FIG. 1. In this manner, the firstand second foot portions define an enlarged open region 49 relative tothat of FIG. 1. As with FIG. 2 a, the embodiment of FIG. 2 b includes afoot extension 40 having an increased average width and taperedcircumferentially-adjacent strut members, as well as alongitudinally-aligned apex 30 a circumferentially adjacent to the toeportion 48 of the foot extension 40 for enhanced retention on a balloondelivery system.

FIG. 2 c depicts an alternative preferred embodiment of the footextension of the present invention. The foot extension 40 of thisembodiment is provided with a generally rectilinear configuration,including a first foot portion 41 extending from the ankle portion 44 tothe toe portion 48 of the foot extension, and a second foot portion 43extending from the heel portion 42 to the toe portion 48. Particularly,the second foot portion defines a contoured base portion 46, such as agenerally V-shape including a first portion 46′ and a second portion46″. In this manner, the foot extension can be configured to provide anadditional area of flexure for expansion of the annular element ifdesired, as well as to define a connection location forlongitudinally-adjacent annular elements as described further below.

As with the embodiments of FIGS. 2 a and 2 b, the first and second footportions 41, 43 of FIG. 2 c are provided with an increased width tostiffen the apex defined by the foot extension 40, and thus control, andmore preferably, balance expansion of the annular element 10. Forexample, in one preferred embodiment, the width W1 of the first footportion 41 and the width W2′ of the first portion 46′ of the V-shapedbase portion are equal to each other, but different than the width W2″of the second portion 46″ of the V-shaped base portion. Unlike theembodiment of FIGS. 2 a and 2 b, which are particularly advantageous incombination with a balloon delivery system, the embodiment of FIG. 2 cdoes not include a longitudinally-aligned apex circumferentiallyadjacent the toe portion of the foot extension. Rather, and asrecognized from FIG. 2 c, at least the apex 30 a locatedcircumferentially proximate the toe portion 48 of the foot extension 40is positioned longitudinally so as to mate with the foot extension whenin the delivery configuration. For example, and as shown in FIG. 2 c,this can be accomplished by providing at least one of the strut members20 of the pair 24 of circumferentially-adjacent strut members with alength greater than the length of the remaining strut members of theannular element. The mating configuration between the foot extension 40and the circumferentially adjacent apex 30 a facilitates a reduced crossprofile of the annular element 10 when in the delivery configuration.This embodiment is particularly advantageous for an endoprosthesis to bedelivered within extremely small vessels, such as certain coronary orneurovascular vessels, or for an endoprosthesis that can be containedwithin a sheath during delivery, such as a self-expanding stent.

FIG. 2 d is a enlarged detail view of a more rounded version of a footextension similar to that of FIG. 2 c, which is depicted with dashedlines for purpose of comparison. Particularly, FIG. 2 d demonstrates theused of more rounded contours to shift or eliminate stressconcentrations that may occur during expansion.

FIG. 2 e depicts another alternative embodiment of a foot extension thepresent invention, which incorporates the mating configuration of thefoot extension and the circumferentially adjacent apex as described withregard to FIG. 2 c. Unlike the embodiment of FIG. 2 c, however, thestrut members 20 connected to the circumferentially adjacent apex 30 aare provided with a length less than that of the remaining strut membersso as to accommodate the desired mating relationship between the apex 30a and the foot extension 40. Furthermore, FIG. 2 e shows that at leastthe circumferentially adjacent apex 30 a is relaxed, such as byproviding a reduced width, to open at a greater angle and thuscompensate for the decrease of the distance D that would otherwiseresult during expansion due to the reduced length of the correspondingstrut members 20. As previously described, expansion of the annularelement 10 thus can be controlled, and more preferably, balanced. Thestrut members 20 having a reduced length and thecircumferentially-adjacent apex 30 a also can be provided with a reducedwidth if desired as shown in FIG. 2 e.

Additional variations of the foot extension are also contemplated. Forexample, the heel portion of the foot extension can extend in acircumferential direction opposite from the toe, but preferably by adistance less than the distance over which the toe extends in the firstdirection.

Any suitable number of foot extensions can be provided on an annularelement in accordance with the present invention. A single footextension can be provided on an annular element if desired. As shown inthe embodiment of FIG. 1, however, it is preferable to define aplurality of apices of an annular element with foot extensions 40,wherein each foot extension extends between a pair 24 ofcircumferentially-adjacent strut members. The foot extensions can beprovided on both longitudinal sides 12, 14 of the annular element 10 asshown in FIG. 1, or only on a single side of an annular element as shownin FIG. 8. Additionally, and as further shown in FIG. 8, it is possibleto combine an annular element having one or more foot extensions withanother annular element having no foot extension if desired. Theplurality of foot extensions, if provided, can all extend in the samecircumferential direction, or in opposite circumferential directions ifdesired. For example, and as shown in FIG. 1, the foot extensions on onelongitudinal side of each annular element can extend in one directioncircumferentially 17, whereas the foot extensions on the other side ofthe annular element extend in the opposite circumferential direction. Inother embodiments, such as FIG. 6, all foot extensions 40 can extend inthe same circumferential direction, either clockwise or counterclockwisewhen viewed from one end of the endoprosthesis, regardless of thelongitudinal side 12, 14 of the annular elements 10 on which the footextensions 40 are disposed.

When a plurality of foot extensions are provided on an annular element,the foot extensions can be evenly spaced along the corresponding side ofthe annular element as shown in FIG. 1, or can be spaced in a staggeredfashion as shown in FIG. 4. The number of apices that are not defined bya foot extension along the corresponding side of the annular element,and thus disposed between foot extensions, will depend upon the totalnumber of apices desired for the annular element and the total number ofsuch apices to be defined by a foot extension.

Further in accordance with the present invention, and as previouslynoted when a plurality of annular elements is provided, the firstannular element and the second annular element are connected to eachother at a connection location. A single connection location can beprovided between two adjacent annular elements, or a plurality ofconnection locations can be provided as preferred. Furthermore, and asdescribed below, the connection location can include one or moreconnectors extending between adjacent annular elements, or theconnection location can be defined by an overlapping geometric patternof two adjacent annular elements.

Preferably, the connection location includes a foot extension. Aspreviously noted, each foot extension defines at least two areas offlexure. Such areas of flexure generally are located in the ankle, toeor heel portions of the foot extension. As such, the foot extension canfacilitate greater longitudinal flexibility when included at theconnection location between two adjacent annular elements. The multipleareas of flexure of the foot extension can also compensate forforeshortening when disposed at the connection location. As the annularelement is expanded, the foot extension can be configured to open in amanner to adjust or compensate for some or all of the change that occursin the longitudinal dimension of the annular element. That is, the footextension can be configured to have a first longitudinal dimension whenin the delivery configuration, and to straighten or retract, as deemednecessary, so as to have a second longitudinal dimension when in thedeployed configuration. The difference between the first longitudinaldimension and the second longitudinal dimension of the foot extensionpreferably is substantially equivalent to the corresponding change inthe longitudinal dimension of the annular element. Similarly, the footextension can be stiffened by increasing the width of one or both of thefirst and second foot portions, or by otherwise altering the geometry ofthe foot extension in a suitable manner, to reduce the amount in whichthe foot extension opens, and thus reduce the extent of relatedforeshortening that occurs at the connection location.

Additionally, when located on a corresponding side betweenlongitudinally-adjacent annular elements, the foot extension of oneannular element includes a base portion generally facing the otherannular element. The base portion provides an elongated region in whicha connection location can be disposed, thus increasing versatility fordesign alternatives. For example, one alternative for increasingcoverage provided by a stent is to configure corresponding zig-zag orsinusoidal patterns of longitudinally-adjacent annular elements lessthan 180 degrees out of phase with each other. That is, with the firstside of a first annular element longitudinally adjacent the second sideof a second annular element, it can be desirable for the apicesproximate the first side of the first annular element to becircumferentially out of alignment with the apices proximate the secondside of the second annular element. The foot extensions of the presentinvention allow such circumferential offset between longitudinallyadjacent apices, even without the use of a connector. The foot extensionof the present invention therefore enables greater axial flexibility,foreshortening compensation, radial expansion and coverage of theendoprosthesis.

With reference again to FIG. 1, a plurality of connectors 60 areprovided to connect adjacent annular elements 10 at a plurality ofconnection locations 50. Each connection location 50 of FIG. 1 includesa foot extension 40 of one annular element and an apex 30 of anotherannular element, with a connector 60 having opposite ends 62 connectedtherebetween. If desired, however, the connection location 50 can extendfrom a foot extension to a foot extension, or from an apex to an apex,or to a strut member of one or both annular elements if desired. Asembodied in FIG. 1, each foot extension 40 generally has acircumferentially elongated base portion 46 facing an adjacent annularelement 20. With a connector 60 extending longitudinally from the baseportion 46 of a foot extension 40 to an apex 30, thelongitudinally-adjacent apices 30 of adjacent annular elements arecircumferentially out of alignment. The foot base portions 46 at thelongitudinal ends 102, 104 of the endoprosthesis 100 face outward fromthe remainder of the structure. Preferably, one or more foot extensionsat either end 102, 104 of the endoprosthesis includes an area thatundergoes minimal deformation or strain, such as the base portion 46,when expanded to the deployed configuration. A wire or strip ofradiopaque material can be wrapped around or otherwise secured to thisarea of minimal strain so as to act as a radiopaque marker 120 forimaging purposes. Alternatively, a marker tab or eyelet can be attachedat one or both ends of the endoprosthesis as described in detail withreference to FIG. 25, below.

For simplicity and clarity, each connector depicted in FIG. 1 is astraight member. It is recognized, however, that the connector can becontoured or shaped to increase longitudinal flexibility if desired, asshown in FIGS. 11-13 and described further below. Similarly, theconnectors need not extend parallel to the longitudinal axis, but can bealigned diagonally or helically such that the ends of the connector arecircumferentially offset as shown for purpose of example in FIGS. 14 band 14 d-14 e.

A variety of design alternatives for different endoprosthesisembodiments can be achieved by selectively combining the various aspectsof the present invention. For purpose of illustration and notlimitation, a number of exemplary embodiments including the combinationof connectors with foot extensions of the present invention are depictedin planar format in FIGS. 3-10. As with the embodiment of FIG. 1, theconnectors are depicted as straight members for clarity and simplicity,but any connector configuration can be used as desired.

The embodiment of FIG. 3, shown in a deployed configuration, is similarto that of FIG. 1, but includes a connector extending from each footextension 40 of one annular element 10 to a longitudinally adjacent apex30 of another annular element. As previously noted, the endoprosthesisof the invention can be formed as a rolled sheet or similar coiledstructure if desired. As depicted in FIG. 3, complimentary lateral edges106, 108 can be defined by providing connection locations 50continuously in longitudinal alignment along the length of theendoprosthesis 100. Particularly, the connectors 60 and correspondingfoot extensions 40 of the connection locations along the lateral edges106, 108 define interlocking projections 109. The endoprosthesis 100 ofthis embodiment can be delivered in a contracted, coiled state to adeployment site with the lateral edges 106, 108 overlapping each other.Upon deployment, the endoprosthesis 100 will unravel from its coiledstate, as well as expand circumferentially from its contracted state dueto expansion of the annular elements. Once deployed, the interlockingprojections 109 along the lateral edges will engage the “cells” 105defined in the overlapping layer upon the application of a compressiveforce to prevent collapse of the endoprosthesis. A “cell” 105 is theopening formed between two circumferentially adjacent connectionlocations as defined by the closed boundary created by theinterconnected struts, and the foot extensions and connectors asprovided. Alternative arrangements can be used to define interlockingprojections or, if the annular elements are provided with sufficientradial bias or rigidity, no interlocking projections need be provided.

The embodiment of FIG. 4, shown in a slightly deployed configuration,has free foot extensions 40 a, which are longitudinally free from orunconnected to adjacent annular members, and connected foot extensions40 b, which are connected to adjacent annular members 10 with connectors60. The free foot extensions 40 a are aligned in the circumferentialdirection at an angle of about 90 degrees to the longitudinal axis andhave substantially slit-shaped foot regions 49 a. The connected footextensions 40 b have enlarged foot regions 49 b, for greater radialexpansion of the pair 24 of connected strut members, and extendcircumferentially at an angle of less than 90 degrees from thelongitudinal axis 15. The connection locations 50 are disposed atselected apices 30 and partway along the foot base portion 46. The footbase portions 46 of the connected foot extensions 40 b have two portions46′, 46″ oriented at an angle to each other to affect an area of flexureupon expansion.

One longitudinal side 12 or 14 of each annular element 10 has pairs ofimmediately adjacent connection locations 50. The other longitudinalside of each annular element 10 has connection locations 50 that arespaced from each other by a plurality of apices 30. Additionally, thefoot extensions 40 a, 40 b are unevenly spaced along each annularelement 10. Some strut numbers 20 have foot extensions at either end 22thereof, other strut members 20 include a foot extension 40 a, 40 b onlyat one end, and yet others do not have a foot extension at either end.

As with the embodiment of FIG. 4, the embodiment of FIG. 5 has connectedfoot extensions 40 b with foot regions 49 that are significantly largerthan the foot regions 49 of the free foot extensions 40 a. In thisembodiment as shown in a slightly deployed configuration selected apices30 that are not defined by a foot extension protrude longitudinally morethan other such apices for increased coverage. Additionally, theadjacent annular elements are substantially “in phase”, such thatlongitudinally-adjacent apices of adjacent annular elements arecircumferentially offset from each other. The circumferential extent ofthe connected foot extensions 40 b allows the annular members to beconnected in phase. Thus, the portion 48 of the connected foot members40 b preferably extends circumferentially at least or greater than thecircumferential station of the connection location of the adjacentannular element 10.

The embodiment of FIG. 6 includes opposing and connected foot extensions40 with substantially open foot regions 49. In the deliveryconfiguration shown in FIG. 6, each apex 30 a that iscircumferentially-adjacent a foot extension 40 is positioned to matewith the foot extension in a manner similar to that of FIG. 2 c. Also,when in the delivery configuration, the strut members 20 aresubstantially aligned with the longitudinal axis 15 as shown. Theembodiment of FIG. 7 is similar to that of FIG. 6, except footextensions 40 on each annular element 10 circumferentially spaced so asnot to include two foot extensions on a single strut member 20.

In the embodiment of FIG. 8, which is shown substantially in thedelivery configuration, the foot extensions 40 are disposed only on onelongitudinal side of each annular element 10. Preferably, all the footextensions extend in the same longitudinal and circumferentialdirections. It is noted that connection locations 50 are evenly spacedcircumferentially, with two unconnected apices 30 betweencircumferentially adjacent connection locations. Each connectionlocation 50 includes a foot extension 40 on one annular element 10 andan apex 30 on the adjacent annular element 10. Furthermore, theconnection locations 50 between adjacent annular elements 10 arecircumferentially offset from one set of connected annular elements tothe next.

FIGS. 9 and 10 depict alternative embodiment in the deliveryconfiguration, wherein connection locations 50 include connectors 60extending between apices 30 not defined by foot extensions. All of thefoot extensions 40 are free or unconnected. In FIG. 9, all footextensions 40 extend in the same circumferential direction; in FIG. 10,the foot extensions 40 alternate between clockwise and counterclockwisedirections.

As previously noted, FIGS. 1 and 3-10 depict various endoprosthesisembodiments that include a straight connector between adjacent annularelements for purpose of simplicity and clarity. It is understood,however, that alternative connector shapes can be used within the scopeof the invention. For example, FIG. 11 shows an endoprosthesis in thedelivery configuration, which includes a plurality of annular elementsconnected by substantially sinusoidal connectors 60. Each annularelement 10 includes a plurality of interconnected strut members 20,wherein every other apex disposed along a longitudinal side 12 and 14 isdefined by a foot extension 40. Each sinusoidal connector 60 extendsbetween a foot extension 40 on one annular element and an apex 30 on anadjacent annular element. The sinusoidal connector includes curvedportions 64 between the first and second ends 62′, 62″ of the connector60. In this manner, the longitudinally-adjacent apices of adjacentannular elements can be arranged in circumferential alignment with eachother (that is, 180 degrees out of phase) or out of alignment with eachother, as preferred. FIG. 12 a is directed to an endoprosthesisembodiment similar to that of FIG. 11, however, U-shaped connectors,each including a curved portion 64, are provided in lieu of thesinusoidal connectors. In a further embodiment of the invention, asshown in a slightly deployed configuration in FIG. 12 b, anendoprosthesis is provided with a connector 60 between foot extensions40 on longitudinally adjacent apices 30 of adjacent annular elements 10,in a manner similar to the embodiment of FIG. 6. At least oneunconnected apex 30 is disposed between circumferentially adjacent footextensions 40 on each side of the annular element 10. In thisembodiment, however, each connector 60 has a U- or V-shape with at leastone curved portion 64. If desired, the curved portions 64 can all extendin the same circumferential direction, as shown in FIG. 12 a, or canalternate in circumferential direction from one set of adjacent annularelements to the next as shown in FIG. 12 b. Furthermore, and as depictedin FIG. 12 b, the number of connectors, and thus connection locations,between adjacent annular elements can be varied for varied longitudinalflexibility along the length of the endoprosthesis. In another preferredembodiment of the invention an endoprosthesis is provided with thesinusoidal shaped connectors between adjacent annular elements locatedproximate at least one region of the endoprosthesis as shown in FIG. 11,and with the U-shaped connectors between adjacent annular elementslocated proximate another region of the endoprosthesis, as shown in FIG.12 a.

In accordance with an additional aspect of the invention, and as shownin FIG. 13, an alternative connector 60 is provided having an L-shapedportion 66 between its first and second ends 62. The L-shaped portionhas a first leg 66′ and a second leg 66″. A bend or circumferential peak67 is provided between the first and second legs. Preferably, and asshown in FIG. 13, the length of the first leg 66′ is different than thatof the second leg 66″. The width of the first leg 66′ likewise can bedifferent than that of the second leg 66″, as shown if FIG. 13. It ispreferred that the L-shaped connector be connected between adjacentannular elements 10, such that the first end 62′ of the connector 60 iscircumferentially offset from the second end 62″ of the connector 60.FIG. 13 depicts the L-shaped connectors incorporated in anendoprosthesis embodiment similar to that of FIGS. 11 and 12, as shownin the delivery configuration, wherein all of the L-shaped connectorsare arranged so as to extend circumferentially in the same direction, asdefined by the direction in which the bend 67 of the L-shaped portion 66extends.

The L-shaped connector of this aspect of the invention can be configuredto compensate for foreshortening of the endoprosthesis upon deployment,without altering the angle between the first and second legs. That is,the L-shaped connector can be arranged so as to have a firstlongitudinal dimension when in the delivery configuration, and to rotaterelative to the annular elements, as deemed necessary, so as to have asecond longitudinal dimension when in the deployed configuration. Thedifference between the first longitudinal dimension and the secondlongitudinal dimension of the L-shaped connector preferably issubstantially equivalent to the corresponding change in the longitudinaldimension of the annular element to be compensated upon deployment.Rotation of the L-shaped connector can be accomplished or enhanced byweakening the points of connection at either end of the connector withthe corresponding annular elements. Furthermore, the degree ofcompensation, as well as longitudinal flexibility, can be varied byvarying the length of the connectors as shown in FIG. 13.

FIGS. 14 a through 14 e show alternative arrangements of the L-shapedconnector of the present invention as disclosed in U.S. patentapplication 60/379,593, which is incorporated in its entirety herein byreference. Particularly, and as shown in FIGS. 14 a through 14 e, aplurality of L-shaped connectors can be provided between adjacentannular elements 10 such that selected connectors 60 are arranged toextend circumferentially in opposite directions, as defined by thedirection in which the bend 67 of the L-shaped portion is directed. Inthis manner, the strut members 20 of the annular elements 10 and theconnectors form a generally repeating pattern defined by two different,alternating cell shapes. In each embodiment, however, it is recognizedthat the number of connectors and apices, as well as the dimensions ofthe components and the angle of alignment between the legs of theL-shaped portion and between the ends of the connector, can be varied toachieve desired characteristics of the stent such as scaffolding,coverage, and flexibility. Although not shown, one or more of the apicesof each of these embodiments can be defined by a foot extension inaccordance with the invention.

For example, FIG. 14 a shows circumferentially adjacent L-shapedconnectors extending in opposite circumferential directions, whereineach connector 60 is connected between longitudinally adjacent apices 30of adjacent annular elements 10. FIGS. 14 b and 14 d show alternativeembodiments of an endoprosthesis having L-shaped connectors, wherein thecircumferentially-adjacent connectors 60 extend from circumferentiallyadjacent apices 30 on one annular element 10 to non-adjacent apices 30on the other annular element 10. In FIG. 14 c, the L-shaped connectorsextend from respective apices 30 of annular elements 10 to anintermediate location on respective strut members 20 of the annularelements 10. In FIG. 14 e, two connectors extend from the same apex 30of one annular element 10 to different apices 30 on the other annularelement 10. Alternatively, connectors can extend from strut member tostrut member without being connected to peaks of the annular members, ortwo or more connectors can extend from the same apex of both annularelements, respectively. Although each of these embodiments depict theselected connectors extending in opposite circumferential directions, itis recognized that the connectors can all be arranged in the samedirection as previously shown in FIG. 13.

Furthermore, the connector peaks 67 can be aligned longitudinally witheach other in the circumferential direction, i.e., located on the sametransverse plane of the endoprosthesis, but need not be so aligned. Inthe embodiments having connector peaks that are not aligned, it iscontemplated that the endoprosthesis may be more completely or uniformlycrimped if the connector peaks 67 extend circumferentially in oppositedirections as shown in FIG. 14 a, because the peaks of adjacentconnectors will not interfere with each other. Furthermore, theconnection locations 50 and the connectors 60, if present, onlongitudinally-adjacent annular elements 10 are preferablycircumferentially displaced with respect to each other to improveflexibility of the stent. However, all of the connection locations canbe aligned, if desired.

In addition to changing connector shapes, other aspects of theconnectors can be altered to facilitate desired performancecharacteristics for the endoprosthesis. For example, the length andcross-sectional dimensions (e.g., width, thickness) of the connectorscan be varied as shown in FIG. 13, or the number of connectors betweenadjacent annular elements can be increased or decreased to alterlongitudinal flexibility and coverage accordingly. Hence, longitudinalflexibility can be uniform or varied across the length of theendoprosthesis, as desired.

Further in accordance with an additional aspect of the invention, and aspreviously noted, the connection location betweenlongitudinally-adjacent annular elements need not include a separateconnector. Indeed, the connection location can be defined by anoverlapping geometric pattern of two adjacent annular elements. Asdefined herein, “overlapping geometric pattern” and “overlappingpattern” reference the resulting pattern or configuration from two orpatterns arranged to share a common surface or area; it does not suggestor require that this overlapping pattern result in an increase inthickness or material of construction. Preferably, the connectionlocation includes a foot extension.

For purpose of illustration and not limitation, reference is made toFIG. 15, which shows an endoprosthesis substantially similar to that ofFIG. 1, but without separate connectors. FIG. 15 shows an endoprosthesisin a deployed configuration including a plurality of annular elements10, each having first and second longitudinal sides 14, 16 with selectedapices defined by foot extensions 40 extending in oppositecircumferential directions. Connection locations 50 between thelongitudinally-adjacent annular elements 10 are provided by directconnections between opposing foot extensions 40. As shown in thisembodiment, each connection location 50 is generally disposed along thebase portion 46 of each foot extension 40 proximate the toe portion 48,and aligned diagonally or helically along the length of theendoprosthesis. Each foot extension 40 of this embodiment can beconstrued to define a three point hinge configuration defined generallyat the at the toe, heel, and ankle portions 48, 42, 44. Furthermore, andas noted with regard to FIG. 1, one or more foot extensions at eitherend 102, 104 of the endoprosthesis includes an area that undergoesminimal deformation or strain, such as the base portion 46, whenexpanded to the deployed configuration. A wire or strip of radiopaquematerial can be wrapped around or otherwise secured to this area ofminimal strain so as to act as a radiopaque marker 120 for imagingpurposes during delivery and deployment.

In this embodiment, the strut members 20 that are circumferentiallyadjacent the foot extensions 40 and within the circumferential extensionof the foot extensions 40 when in the delivery configuration aredimensioned so the corresponding apices 30 a mate with the footextension 40 as described with regard to the foot extensions of FIG. 2c. For example, FIG. 15 shows two pairs of short strut members 20 ainterconnected sequentially to a medium-length strut member 20 b, alonger strut member 20 c, a medium-length strut member 20 b, two pairsof short strut members 20 a, which connects to the next foot extensions40. In the delivery configuration, the medium and longer strut membershave apices 30 a therebetween that are circumferentially displaced fromthe toe extensions 40.

As with the endoprosthesis embodiments that include a connector for eachconnection location, a wide variety of alternative endoprosthesisembodiments without connectors at the connection locations are likewisewithin the scope of the invention. Particularly, and as previouslynoted, at least one of the first and second foot portions of the footextension defines a base portion generally facing alongitudinally-adjacent annular element. By defining the connectionlocation as an overlapping pattern of the base portion and acorresponding portion of the longitudinally-adjacent annular element, asshown schematically in FIG. 26 for clarity, no connector is required.Additionally, and as previously noted, the generally elongate area ofthe base portion further enables versatility in the circumferentialalignment adjacent annular elements, and the multiple areas of flexureof the foot extension enable enhanced longitudinal flexibility betweenadjacent annular elements without the need for connectors. Furthermore,by eliminating the connectors, an endoprosthesis having more uniformcoverage for scaffolding as well as for the delivery of a drug orsimilar beneficial agent, as described further below, can be provided.

A variety of design alternatives for different endoprosthesisembodiments without connectors can be achieved by selectively combiningthe various aspects of the present invention. For purpose ofillustration and not limitation, as well as for comparison with theembodiment of FIG. 15, a number of exemplary embodiments including thecombination of foot extensions and overlapping patterns at connectionlocations of the present invention are depicted in planar format inFIGS. 16-26.

The embodiment of FIG. 16, shown substantially in a deliveryconfiguration, includes a plurality of annular elements 10, wherein eachlongitudinal side of an annular element has 16 apices. In thisembodiment, four apices on a selected side, e.g. 12, of adjacent annularelements 10 are defined by a foot extension 40, wherein the footextensions 40 extend in the same longitudinal direction but in alternatecircumferential directions from one annular element 10 to the next. Eachfoot extension 40 is configured substantially similar to that of FIG. 2c, wherein the base portion 46 is contoured to include first and secondportions. The contoured pattern of the base portion 46 of each footextension 40 overlaps with the pattern of an apex 30 of thecircumferentially-adjacent annular element. Hence, four connectionlocations 50 are provided between longitudinally-adjacent annularelements 10, with three apices 30 disposed between the connectionlocations 50 along the corresponding longitudinal side 12, 14 of eachannular element 10. The annular element 10 at the longitudinal end 102of the endoprosthesis 100 in which the foot extensions 40 are directedis free of foot extensions 40. FIG. 17 shows an alternative embodimentsimilar to that of FIG. 16, wherein the lengths of the strut members 20disposed circumferentially between the foot extensions 40 are varied toreduce the gap area defined between longitudinally-adjacent annularelements 10, and thus increase coverage.

FIG. 18 shows an alternative embodiment similar to that of FIG. 16,wherein the center apex disposed along the longitudinal side 12, betweenthe foot extensions 40 b that define connection locations is defined asa foot extension 40 a. In this manner, circumferentially-adjacent footextensions 40 along a longitudinal side of an annular element 10 areseparated by single apex 30, wherein every other foot extension 40 bforms a connection location with an apex 30 of a longitudinally-adjacentannular element 10. FIG. 19 shows an enlarged detail of an embodimentsimilar to FIG. 18, in the delivery configuration, wherein the baseportion 46 of each foot extension 40 has an increased average width aspreviously discussed with regard to FIG. 2 c. Particularly, the baseportion 46 of each foot extension 40 is contoured with a generallyV-shape to include a first portion 46′ and second portion 46″. Thesecond portion 46″ proximate the toe portion has a width greater thanthe first portion 46′ as previously discussed. Furthermore, the footextensions 40 of FIG. 19 are all directed in the same circumferentialdirection.

The embodiment of FIG. 20, which is shown substantially in a deliveryconfiguration, includes 18 apices on each longitudinal side 12, 14 ofeach annular element 10. On each longitudinal side of an annular element10 that faces an adjacent annular element, three pair of apices aredefined by a pair of foot extensions 40 with each pair of footextensions 40 having an apex 30 a disposed therebetween. Furthermore,each pair of foot extensions 40 includes one foot extension 40 b at aconnection location 50 with a foot extension 40 b on a correspondingside of a longitudinally-adjacent annular element 10. Hence, threeconnection locations 50 are provided between adjacent annular elements10. Each foot extension 40 has a generally enlarged foot region 49.Particularly, each foot extension 40 at a connection location 50 has acontoured base portion 46 similar to that of FIG. 16, although moreelongate in the longitudinal direction. The connection location 50 isthus defined by the overlapping base portions of the corresponding footextensions 40 b. It is noted that the foot extensions 40 a that share acommon strut member 20 in this embodiment are not at connectionlocations 50. The three pairs of foot extensions on each side 12, 14 areseparated from each other in this embodiment by three apices 30.

FIG. 21 shows an embodiment, substantially in a delivery configuration,including 18 apices on each side of each annular element 10, whereinevery other apex on a side facing an adjacent annular element 10 isdefined by a foot extension 40. Three pairs of circumferentiallyadjacent foot extensions 40 b are connected to three corresponding pairsof foot extensions 40 b on a longitudinally-adjacent annular element, soas to define six connection locations 50 as shown. Hence, threeremaining foot extensions 40 a on each side of the annular element 10are interspersed between the three pair of foot extensions 40 b of theconnection locations 50. The foot extensions 40 on each side of theannular elements 10 extend in the same circumferential direction, but ina direction opposite the foot extensions 40 disposed on the oppositelongitudinal side of the annular element 10.

FIG. 22 shows an embodiment similar to that of FIG. 18, however, eachannular element includes additional strut members and apices.Particularly, the embodiment of FIG. 22 includes 20 apices, rather than16 apices, on each side of each annular element 10, with every otherapex defined by a foot extension 40. Hence, five connection locations 50are defined between adjacent annular elements 10. The embodiments ofFIGS. 23 and 24 are similar to the embodiment of FIG. 22; however,selected apices 30 s of one annular element are longitudinally alignedto be disposed between circumferentially adjacent foot extensions 40 ofan adjacent annular element. As previously noted, and in accordance withthe invention, the apices on longitudinally adjacent sides of adjacentannular elements 10 can be disposed so as to be circumferentially out ofalignment with each other. Hence, the strut members 20 s that areinterconnected at the apices 30 s disposed between adjacent footextensions 40 of an adjacent annular element, are provided with agreater length than the remaining strut members so as to dispose theapex 30 s generally between the foot extensions 40. In this manner,resulting coverage and scaffolding can be increased. Each of FIGS. 22-24is shown substantially in a delivery configuration.

FIG. 25 discloses an embodiment in a slightly deployed configurationhaving eight apices per side of each annular element 60. Each annularelement 10 is arranged in a diagonal format to define a 360 degree turnof a helical pattern. In this manner, the circumferential end 18 of oneannular element can be joined with the corresponding circumferential end16 of a longitudinally-adjacent element to form a continuous helicalpattern along the length of the endoprosthesis 100. Two apices on oneside of each annular element are defined by foot extensions 40 similarto that of FIG. 2B. Each foot extension 40 forms an overlapping patternwith the an apex 30 on a circumferentially adjacent side of an adjacentannular element. Hence, two connection locations 50 are defined betweenadjacent annular elements 10. As previously noted with regard to FIG.2B, the apex 30 a circumferentially adjacent to the foot extension 40 islongitudinally positioned to substantially contact the toe portion 48when in the delivery configuration to increase coverage, as well as tocapture balloon material if desired. The embodiment of FIG. 25 alsoincludes an eyelet or tab to incorporate a radiopaque marker 120 at oneor both ends 102, 104 of the endoprosthesis if desired. Alternativetechniques for incorporating radiopaque material are described below.

FIG. 26 is an enlarged view of a connection location similar to that ofFIG. 25, wherein the overlapping geometric pattern of a connectionlocation is schematically depicted for purpose of illustration.Particularly, FIG. 26 shows an annular element having a foot extensionsimilar to that of FIG. 2 a. The pattern of the foot extension 40 balong the base portion 46 is aligned longitudinally to overlap with aportion of the pattern of a circumferentially adjacent annular element10. The resulting configuration of the overlapping pattern defines theconnection location 50 between the two annular elements 10. The amountor extent of overlap between the two patterns can be varied as desired.For example, the patterns can be substantially in tangential contact, orcan be fully overlapping. Additionally, fillets or a similar transitioncan be included to smooth or eliminate any sharp or abrupt edges. It isnoted that the thickness at the juncture defined by the overlappingpatterns need not be, and preferably is not, increased. Rather, theoverlapping pattern refers to the resulting configuration when twoseparate patterns share a common surface or area.

FIGS. 27 a through 27 d show alternative connection locations 50 definedby different degrees of geometrical overlap between adjacent annularelements 10. The connected foot extension 40 b and apex 30 of FIG. 27 ahave a slight geometrical overlap, such as a tangential surface contact.FIG. 27 b shows an overlapping pattern, wherein the connected apex 30and foot extension 40 b fully overlap to substantially share a commonmember. As depicted, the apex 30 at the connection location 50 extendslongitudinally further than the unconnected apices 30. In FIG. 27 c, theapex 30 at the connection location 50 protrudes into the foot region ofthe corresponding foot extension 40 b. In this embodiment, the footextension 40 b is generally enlarged and rounded at the base portion 46compared to free foot extensions 40 a to stiffen and reinforce theconnection location 50. Additional areas of flexure can be defined bythe contour of this configuration, as compared to that of the other footextensions. By contrast, connected foot extension 40 b of FIG. 27 dincludes a flattened base portion 46 substantially perpendicular to thelongitudinal axis to define a more relaxed configuration. As with FIG.27 c, the connected apex 30 of this embodiment overlaps with the footextension 40 b and protrudes into the foot region 49.

As noted above, the various aspects of the present invention allow for avariety of different endoprosthesis embodiments, based upon selectivecombinations of the features previously described and shown. Similarly,the endoprosthesis of the present invention can be made using any of anumber of known manufacturing techniques and materials.

The material of construction is preferably selected according to theperformance and biological characteristics desired. For example, theendoprosthesis of the invention can be made to be expanded by the changeof a delivery condition, such as by the removal of a restraint orexposure to the environment within the body lumen, so as to be selfexpanding, or by the application of an external force or energy, such asby a balloon or by a radio frequency. For purpose of illustration andnot limitation, reference is made generally to “self-expanding”embodiments and “balloon expandable” embodiments of the endoprosthesisof the present invention.

Self-expanding embodiments can be made from any of a variety of knownsuitable materials including super elastic or shape memory materials,such as nickel-titanium (NiTi) alloys, Elgiloy, and suitable polymers,such as suitable shape memory polyurethane copolymers, or anyequivalents thereof. An endoprosthesis made of a suitable super elasticmaterial can be compressed or restrained in its delivery configurationon a delivery device using a sheath or similar restraint, and thendeployed to its deployed configuration at a desired location by removalof the restraint as is known in the art. An endoprosthesis made of shapememory material generally can be delivered in a like manner, and ifthermally sensitive, can be deployed by exposure of the endoprosthesisto a sufficient temperature to facilitate expansion as is known in theart. It also is possible to make the self-expanding embodiment of abiocompatible material capable of expansion upon exposure to theenvironment within the body lumen, such as a suitable hydrogel orhydrophilic polymer, including biodegradable or bioabsorbable polymers,such as polycaprolactone (PCL), poly-D,L-lactic acid, Poly-L-lacticacid, poly(lactide-co-glycolide), poly(hydroxybutyrate), polyanhydrides,poly(glycolic acid). For example, if made of an expandable hydrophilicmaterial, the endoprosthesis can be delivered to the desired location inan isolated state, and then exposed to the aqueous environment of thebody lumen to facilitate expansion. Alternative known delivery devicesand techniques for a self-expanding endoprosthesis likewise can be used.

Balloon expandable embodiments or the like can be made of any of avariety of known suitable deformable materials, including stainlesssteel, silver, platinum, cobalt chromium alloys such as L605, MP35N orMP20N or any equivalents thereof. “L605” is understood to be a tradename for an alloy available from UTI Corporation of Collegeville, Pa.,including about 53% cobalt, 20% chromium and 10% nickel. “MP35N” and“MP20N” are understood to be trade names for alloys of cobalt, nickel,chromium and molybdenum available from Standard Press Steel Co.,Jenkintown, Pa. MP35N generally includes about 35% cobalt, 35% nickel,20% chromium, and 10% molybdenum. MP20N generally includes about 50%cobalt, 20% nickel, 20% chromium and 10% molybdenum. For delivery, theendoprosthesis of a suitable material is mounted in the deliveryconfiguration on a balloon or similar expandable member of a deliverydevice. Once properly positioned within the body lumen at a desiredlocation, the expandable member is expanded to expand the endoprosthesisto its deployed configuration as is known in the art. Additionally, oralternatively, balloon expandable embodiments can be made of suitablebiocompatible polymers, including biodegradable or bioabsorbablematerials, which are either plastically deformable or capable of beingset in the deployed configuration. If plastically deformable, thematerial is selected to allow the endoprosthesis to be expanded in asimilar manner using an expandable member so as to have sufficientradial strength and scaffolding and also to minimize recoil onceexpanded. If the polymer must be set in the deployed configuration, theexpandable member can be provided with a heat source or infusion portsto provide the required catalyst to set or cure the polymer. Alternativeknown delivery devices and techniques for a self-expandingendoprosthesis likewise can be used.

Additional materials or compounds also can be incorporated into or onthe endoprosthesis if desired. For example, the endoprosthesis can beprovided with one or more coatings of biocompatible material to enhancethe biocompatibility of the device. Such coatings can include hydrogels,hydrophilic and/or hydrophobic compounds, and polypeptides, proteins oramino acids or the like, including poly vinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), parylene, and heparin. A preferred coating materialincludes phosphorylcholine, as disclosed in U.S. Pat. Nos. 5,705,583 and6,090,901 to Bowers et al. and U.S. Pat. No. 6,083,257 to Taylor et al.,each of which is incorporated by reference herein. Such coatings canalso be provided on the endoprosthesis to facilitate the loading ordelivery of beneficial agents or drugs, such as therapeutic agents,pharmaceuticals and radiation therapies. Alternatively, the surface ofthe endoprosthesis can be porous or include one or more reservoirs orcavities formed therein to retain beneficial agent or drug therein as isknown in the art. For purposes of illustration and not limitation, thedrug or beneficial agent can include antithrombotics, anticoagulants,antiplatelet agents, thrombolytics, antiproliferatives,anti-inflammatories, agents that inhibit hyperplasia, inhibitors ofsmooth muscle proliferation, antibiotics, growth factor inhibitors, orcell adhesion inhibitors, as well as antineoplastics, antimitotics,antifibrins, antioxidants, agents that promote endothelial cellrecovery, antiallergic substances, radiopaque agents, viral vectors,antisense compounds, oligionucleotides, cell permeation enhancers, andcombinations thereof.

The endoprosthesis can also be provided with coverings, such as PTFE,ePTFE, Dacron, woven materials, cut filaments, porous membranes, orothers such materials to form a stent graft prosthesis. Similarly, amedical device, such as a valve, a flow regulator or monitor device, canbe attached to the endoprosthesis, such that the endoprosthesisfunctions as an anchor for the medical device within the body lumen.

Additionally, an imaging compound or radiopaque material can beincorporated with the endoprosthesis. For example, one or more of theannular elements of the endoprosthesis can be made of a suitableradiopaque material, such as gold, tantalum or a similar material.Alternatively, the radiopaque material can be applied on selectedsurfaces of one or more of the annular elements using any of a varietyof known techniques, including cladding, bonding, adhesion, fusion,deposition or the like. In a preferred embodiment, the material used forfabrication of the endoprosthesis includes a composite structure havingmultilayers of different materials or compositions. Generally, at leastone layer is a base material such as stainless steel, nickel-titaniumalloy or cobalt chromium alloy to impart the intended structuralcharacteristic of the endoprosthesis, and at least another layer is aradiopaque material such as gold or tantalum for imaging purposes. Forexample, a tri-layer structure of 316L-Ta-316L is preferred for aballoon expandable stent and a tri-layer structure of NiTi—Ta—NiTi ispreferred for a self-expanding stent. Suitable multi-layerd compositestructures are available in sheet or tube form from UTI Corporation ofCollegeville, Pa., and are disclosed in U.S. Pat. No. 5,858,556, whichis incorporated herein by reference. In yet another embodiment, one ormore marker elements of radiopaque material can be attached to theendoprosthesis. For example, and as previously shown in FIG. 25, eyeletsor tabs can be provided on one or more annular elements, preferably atat least a distal or proximal longitudinal end of the endoprosthesis. Arivet or bead of radiopaque material can then be attached to the eyeletor tab in a manner as known in the art. Alternatively, the separatemarker can be attached directly to annular element. For example, and inaccordance with a preferred embodiment of the invention as shown inFIGS. 1 and 15, a wire or strip of radiopaque material can be wrappedaround and secured to a base portion of one or more foot extensions atone or both longitudinal ends of the endoprosthesis; preferably byproviding the foot extension with a geometry to enable limited strain inthe base portion of the foot extension upon deployment.

A variety of manufacturing techniques are well known and may be used forfabrication of the endoprosthesis of the present invention. For example,and in a preferred embodiment, the endoprosthesis can be formed from ahollow tube of suitable material using a known technique, such as bylaser cutting, milling or chemical etching. The structure ismechanically blasted and then electropolished or otherwise finished toremove burrs and eliminate sharp edges and contaminates. Alternatively,the endoprosthesis can be fabricated from a sheet of suitable materialusing a similar cutting, milling or etching technique, and then rolledor bent about a longitudinal axis into the desired shape. If desired,the lateral edges of the structure can be joined together, such as bywelding or bonding, to form a closed tubular structure, or the lateraledges can remain unattached to form an coiled, rolled sheet or opentubular structure. Conversely, a suitable material of construction canbe applied selectively to a substrate to define the desired pattern ofthe endoprosthesis structure, and then the substrate can be removed.Other methods of manufacture also can be used for the endoprosthesis ofthe present invention, such as by bending toroidal rings or elongatelengths of wire into appropriately shaped members, such as thatcorresponding to each annular element, and then joining theappropriately shaped members together at connection locations by awelding or bonding technique or the like. If a shape memory material isused, such as a nickel titanium alloy, the fabricated structure can beheat treated on a mandrel or the like using known techniques toestablish the desired endoprosthesis shape and dimensions at apredetermined temperature, e.g. when above austenitic transitiontemperature.

As originally cut or fabricated, the endoprosthesis can correspond toits delivery configuration or to a deployed configuration or aconfiguration therebetween. Preferably, however, the endoprosthesis isfabricated with a configuration at least slightly larger than thedelivery configuration as shown in the planar formats of FIGS. 6-10 and16-24, for example. In this manner, the endoprosthesis can be crimped orotherwise compressed into its delivery configuration on a correspondingdelivery device. In another preferred embodiment, the endoprosthesis isoriginally fabricated from a tube having a diameter corresponding to thedeployed configuration. In this manner, the longitudinally-free portionsof the annular elements (e.g., apices not at a connection location) andcircumferentially-free portions (e.g., the toe portion of the footextensions) can be maintained within the general cylindrical shape(e.g., diameter) of the endoprosthesis when deployed, so as to avoidsuch portions from extending radially inwardly when in the deployedconfiguration. The endoprosthesis is therefore designed to match thetarget vessel in which the endoprosthesis is to be deployed. For examplea stent will typically be provided with an outer diameter in thedeployed configuration ranging from about 1 mm for neurological vesselsto about 25 mm for the aorta. Similarly, a stent will typically beprovided with a length ranging from 5 mm to 200 mm. Variations of thesedimensions will be understood in the art based upon the intendedapplication or indication for the endoprosthesis.

As previously noted, the geometry of each component of theendoprosthesis, such as the width, thickness, length and shape of thestrut members and foot portions, as well as of the connectors ifprovided, is preferably selected to obtain predetermined expansion,flexibility, foreshortening, coverage scaffolding, and cross profilecharacteristics. For example, longer strut members can promote greaterradial expansion or scaffolding coverage. The phase difference orcircumferential alignment between adjacent annular elements likewise canbe altered to control coverage and flexibility as well as facilitatemore uniform drug delivery. Similarly, the number and placement ofconnection locations and, if present, the connectors, betweenlongitudinally-adjacent annular elements are preferably selected toobtained the desired flexibility of the endoprosthesis. The number ofapices and foot extensions between connection locations also can bevaried to achieve desired performance characteristics. FIG. 28 depicts arepresentative embodiment depicting such variations within anendoprosthesis of strut lengths and strut widths for varied rigidity,and of connector locations for varied flexibility.

As recognized from the detailed description above, the foot extensionsparticularly enhance and provide versatility in the design of theendoprosthesis of the present invention. The foot extension can beconfigured and dimensioned relative to the strut members and theremainder of the endoprosthesis to compensate for longitudinalforeshortening upon stent expansion. For example, the areas of flexureof the foot extensions can be adjusted by contouring the foot geometryand dimensions, as well as by altering the lengths of selected strutmembers. Alternatively, the geometry of the foot extension can beconfigured to provide a desired amount of lengthening or shortening ofthe endoprosthesis upon expansion. The foot extensions can be configuredto balance or assist in evenly distributing strain or expansion of theendoprosthesis. The foot extensions also can improve and control theflexibility of the endoprosthesis, preferably without substantiallyimpacting the desired coverage or scaffolding of the endoprosthesis. Thecircumferentially elongated base portion of each foot extension providesa wide range of connection locations, and allows adjacent annularelements to be attached over a range of phase differences orcircumferential alignment. The foot extensions can be configured toproduce a torque on longitudinally free portions, such as unconnectedapices, to maintain these longitudinally free portions within thegeneral cross profile of the endoprosthesis when flexed along itslongitudinal axis or expanded to its deployed configuration. Thisfeature can be adjusted if it is desired to embed portions of theendoprosthesis into the vessel wall or other tissue.

Reference is now made to two exemplary preferred embodiments of a stentof the present invention; a self-expanding stent as shown in FIGS. 29 athrough 29 f, and a balloon expandable stent as shown in FIGS. 30 athrough 30 f.

FIG. 29 a shows the planar format of a preferred embodiment of aself-expanding stent as cut and polished in a slightly deployedconfiguration. As depicted herein, the self-expanding stent comprisesten annular elements 10 with five connection locations 50 betweenlongitudinally-adjacent annular elements 10 for an approximate stentlength of about 21 mm. Annular elements can be added to increase thestent length, or omitted to decrease the stent length, as desired. Eachannular element 10 includes fifteen apices per longitudinal side. On onelongitudinal side 12 of each annular element 10, five apices are definedby foot extensions 40. Two circumferentially-adjacent apices 30 arelocated between adjacent foot extensions. On the other longitudinal side14 of each annular element 10, no foot extensions are provided. Eachfoot extension 40 has a shape similar to that of FIG. 2 c, as previouslydescribed in detail. Each of the five connection locations 50 betweenadjacent annular elements 10 is defined by a slightly overlappingpattern of the base portion 46 of each foot extension 40 with acorresponding apex 30 of a longitudinally-adjacent annular element in amanner similar to that of FIG. 27 a. In this manner,longitudinally-adjacent apices of adjacent annular elements are out ofcircumferential alignment with each other so as to be less than 180degrees out of phase. Furthermore, connection locations 50 arecircumferentially displaced or offset from one set of annular elementsto the next.

The self-expanding stent of this preferred embodiment is made from asuitable tube stock of nickel-titanium alloy, such as SE508 or SM508,ASTM Standard F2063-00, comprising about 54.5 to about 57% wt. nickeland about 45.5 to about 42.7% wt. titanium, which is commerciallyavailable from Minitubes, Inc. of Grenoble, France. It is recognized,however, that alternative alloy compositions can be used if desired. Forfabrication of a self-expanding stent having a deployed configurationdiameter of about 7 mm to about 8 mm, the tube stock has an outerdiameter of about 0.091 inch and a uniform wall thickness of about 0.010inch. The tube stock is laser cut with the configuration shown in FIG.29 b as a continuous pattern around the circumference of the tube;wherein only the front half of the structure is shown for clarity. Thecut tube is then mechanical blast and sequentially heat treated on aseries of cylindrical mandrels of increasing diameter using knowntechniques to set the desired deployed configuration of the stent whenin an austenitic state as shown in FIG. 29 d. The heat set stent is thenelectropolished using known techniques. The relevant dimensions of thestrut members for this preferred embodiment, after electropolishing,include a nominal strut length of about 0.055 inch, a nominal strutwidth of about 0.004 inches and a generally uniform thickness of about0.008 inches. Regarding each foot extension, after electropolishing, thefirst portion of the foot extension has a width of about 0.005 inch anda length of about 0.013, as measured along its outer edge, and the baseportion of the foot extension includes total length of about 0.033, asmeasured along its outer edge, with a first portion proximate the heelportion having a width of about 0.005 inch and a second portionproximate the toe portion having a width of about 0.007 inch. The strutmember extending from the ankle portion of the foot extension tapersfrom a width of about 0.005 inch at the end proximate the foot extensionto about 0.004 inch at the opposite end, with a length of about 0.059inch. The strut member extending from the heel portion of the footextension tapers from a width of about 0.005 inch at the end proximatethe foot extension to about 0.004 inch at the opposite end, with alength of about 0.068 inch. After polishing, additional cleaning orpreparation may be required.

Once prepared, the self-expanding stent of this embodiment is compressedto a delivery configuration as shown in the front-half view of FIG. 29c, preferably with the strut members generally parallel to thelongitudinal axis of the stent and each other. The stent can then bedelivered using a conventional retractable sheath delivery catheter, asis known in the art. FIGS. 29 d and 29 e show the self-expanding stentof this embodiment in a deployed configuration. For purpose of clarity,only the front half of the stent is shown in FIG. 29 d. As depicted, thestent of this embodiment has been balanced for generally uniformexpansion. FIG. 29 f shows a self-expanding stent of greater length ofthis embodiment deployed in a curved vessel, wherein the apicesproximate the inner radius of the curve generally open less than theapices proximate the outer radius of the curve.

FIG. 30 a shows the planar format of a preferred embodiment of a balloonexpandable stent as cut and polished in a slightly deployedconfiguration. As depicted herein, the balloon expandable stentcomprises fifteen annular elements 10 with two connection locations 50between longitudinally-adjacent annular elements for an approximatestent length of about 18 mm. Annular elements can be added to increasethe stent length, or omitted to decrease the stent length, as desired.Each annular element includes ten apices per longitudinal side. On onelongitudinal side 12 of each annular element 10, two apices are definedby foot extensions 40. Four circumferentially-adjacent apices 30 arelocated between adjacent foot extensions. On the other longitudinal side14 of each annular element 10, no foot extensions are provided. Eachfoot extension 40 has a shape similar to that of FIG. 2 a, as previouslydescribed in detail. Each of the two connection locations 50 betweenadjacent annular elements 10 is defined by an overlapping pattern of thebase portion 46 of each foot extension 40 b with a corresponding apex 30of a longitudinally-adjacent annular element in a manner similar to thatof FIG. 26. In this manner, longitudinally-adjacent apices of adjacentannular elements are out of circumferential alignment with each other soas to be less than 180 degrees out of phase. Furthermore, connectionlocations 50 are circumferentially displaced or offset from one set ofannular elements to the next.

The balloon expandable stent of this preferred embodiment is made from asuitable tube stock of composite material including an inner layer of316L stainless steel, a middle layer of tantalum, and an outer layer of316L stainless steel, which is available from UTI Corporation ofCollegeville, Pa. It is recognized, however, that alternative materialcompositions can be used if desired. For fabrication of a balloonexpandable stent having a deployed configuration diameter of about 2.75mm to about 3.0 mm, the tube stock has an outer diameter of about 0.062inch and a generally uniform wall thickness of about 0.004 inch, withthe tantalum layer constituting between about 3% to about 50% of thewall thickness, and more preferably between about 10% to about 25% ofthe wall thickness depending upon the intended indication. For example,a coronary stent of this dimension preferably would have a tantalumlayer of between about 15% to about 17% of the tube stock thickness. Thetube stock is laser cut with the configuration shown in FIG. 30 b as acontinuous pattern around the circumference of the tube; only sevenannular elements are depicted for purpose of clarity. The cut tube isthen mechanically blasted and electropolished using known techniques.The relevant dimensions of the strut members for this preferredembodiment, after electropolishing, include a nominal strut length ofabout 0.036 inches, a nominal strut width of about 0.003 inches and agenerally uniform thickness of about 0.003 inches. Regarding each footextension, after electropolishing, the first portion of the footextension has a width of about 0.005 inch and a length of about 0.008inch, as measured along the outer edge, and the base portion of the footextension has a width of about 0.005 inch and a length of about 0.021inch as measure along the outer edge. The strut member extending fromthe ankle portion of the foot extension tapers from a width of about0.004 inch at the end proximate the foot extension to about 0.003 inchat the opposite end, with a length of about 0.034 inch. The strut memberextending from the heel portion of the foot extension tapers from awidth of about 0.005 inch at the end proximate the foot extension toabout 0.003 inch at the opposite end, with a length of about 0.042 inch.After electro polishing, additional cleaning or preparation may berequired.

Once prepared, the balloon expandable stent of this embodiment iscompressed to a delivery configuration as shown in FIG. 30 c, with onlyseven annular elements depicted for purpose of clarity. Preferably, thestrut members are generally parallel to the longitudinal axis of thestent and each other when in the delivery configuration. The stent canthen be delivered using a conventional balloon delivery device, as isknown in the art. Preferably, a portion of balloon material of thedelivery device is captured in the gap defined by the foot extension andthe circumferentially-adjacent strut member. FIGS. 30 d and 30 e showthe balloon expandable stent of this embodiment in a deployedconfiguration; only seven annular elements are depicted for purpose ofclarity. For purpose of clarity, only the front half of the stent isshown in FIG. 30 d. As depicted, the stent of this embodiment has beenbalanced for generally uniform expansion. FIG. 30 f shows the balloonexpandable stent of this embodiment deployed in a curved vessel, whereinthe apices proximate the inner radius of the curve generally open lessthan the apices proximate the outer radius of the curve.

While illustrative embodiments of the invention have been disclosedherein, numerous modifications and other embodiments may be devised bythose skilled in the art in accordance with the invention. For example,the various features depicted and described in the embodiments hereincan be altered or combined to obtain desired endoprosthesischaracteristics in accordance with the invention. Therefore, it will beunderstood that the appended claims are intended to cover all suchmodifications and embodiments, which are within the spirit and scope ofthe present invention.

1. An endoprosthesis for delivery in a body lumen comprising: a firstset of interconnected strut members defining a first annular element,each strut member of the first annular element including a first end anda second end; and a second set of interconnected strut members defininga second annular element, each strut member of the second annularelement including a first end and a second end; and a third set ofinterconnected strut members defining a third annular element, eachstrut member of the third annular element including a first end and asecond end; each annular element aligned longitudinally adjacent to eachother along a longitudinal axis and connected to each other at at leastone connection location, each annular element being expandable between adelivery configuration and a deployed configuration; each of the annularelements including a foot extension extending between at least one pairof circumferentially-adjacent strut members, the foot extensionincluding a first foot portion extending circumferentially from thefirst end of one of the circumferentially-adjacent strut members of thepair and a second foot portion extending circumferentially from thefirst end of the other of the circumferentially-adjacent strut members,the first and second foot portions joined at a toe portion of the footextension and wherein the first end of selectedcircumferentially-adjacent strut members of each annular element areinterconnected to define apices proximate a first longitudinal side ofthe annular element and the second end of selectedcircumferentially-adjacent strut members are interconnected to defineapices proximate a second longitudinal side of the annular element,wherein at least one apex of each annular element is defined by a directinterconnection between circumferentially-adjacent strut members, andfurther wherein each connection location is defined by theinterconnection of the foot extension of one annular element and theapex defined by the direct interconnection betweencircumferentially-adjacent strut members of a longitudinally-adjacentannular element.
 2. The endoprosthesis of claim 1, wherein a pluralityof apices of the annular elements are defined by foot extensions, eachfoot extension extending between a pair of circumferentially-adjacentstrut members.
 3. The endoprosthesis of claim 2, wherein at least onefoot extension extends in a first circumferential direction about thelongitudinal axis and at least another foot extension extends in asecond circumferential direction opposite the first circumferentialdirection.
 4. The endoprosthesis of claim 1, further comprising at leastone connector extending between the first annular element and the secondannular element at the connection location, the connector having a firstend and a second end.
 5. The endoprosthesis of claim 4, wherein theconnector includes an L-shaped portion between the first and secondends, the L-shaped portion including a first leg and asecond leg angledrelative to the first leg.
 6. The endoprosthesis of claim 5, wherein thefirst leg has a length different than a length of the second leg.
 7. Theendoprosthesis of claim 4, wherein the connector includes a curvedportion between the first end and the second end.
 8. The endoprosthesisof claim 1, wherein at least one of the first and second foot portionsincludes a curved portion.
 9. The endoprosthesis of claim 1, wherein atleast one of the first and second foot portions defines a base of thefoot extension, the base generally facing the other of the at least oneof the first and second annular elements.
 10. The endoprosthesis ofclaim 9, wherein the base is defined as a contoured member directedlongitudinally toward the other of the at least one of the first andsecondannular elements.
 11. The endoprosthesis of claim 10, wherein thecontoured member generally has a V-shape.
 12. The endoprosthesis ofclaim 11, wherein a first portion of the V-shape has a width differentthan a second portion.
 13. The endoprosthesis of claim 10, wherein theconnection location includes a connector extending between the baseportion and the other of the at least one of the annular elements. 14.The endoprosthesis of claim 1, wherein the endoprosthesis is a selfexpanding stent.
 15. The endoprosthesis of claim 1, wherein each footextension is connected to an adjacent annular element.
 16. Anendoprosthesis for delivery in a body lumen comprising: a first set ofinterconnected strut members defining a first annular element, eachstrut member of the first annular element including a first end and asecond end; and a second set of interconnected strut members defining asecond annular element, each strut member of the second annular elementincluding a first end and a second end; and a third set ofinterconnected strut members defining a third annular element, eachstrut member of the third annular element including a first end and asecond end; each annular element aligned longitudinally adjacent to eachother along a longitudinal axis and connected to each other at at leastone connection location, each annular element being expandable between adelivery configuration and a deployed configuration; each of the annularelements including a foot extension extending between at least one pairof circumferentially-adjacent strut members, the foot extensionincluding a first foot portion extending circumferentially from thefirst end of one of the circumferentially-adjacent strut members of thepair and a second foot portion extending circumferentially from thefirst end of the other of the circumferentially-adjacent strut members,the first and second foot portions joined at a toe portion of the footextension and wherein the first end of selectedcircumferentially-adjacent strut members of each annular element areinterconnected to define apices proximate a first longitudinal side ofthe annular element and the second end of selectedcircumferentially-adjacent strut members are interconnected to defineapices proximate a second longitudinal side of the annular element, andfurther wherein each connection location is defined by theinterconnection of the foot extension of one annular element with thefoot extension of a longitudinally-adjacent annular element.
 17. Theendoprosthesis of claim 16, wherein each foot extension is connected toan adjacent annular element.